An Indian Creek, or Pure Gold in .660 shooting Hevi-13 3" 2oz #6's has been a proven winner for me. I have also had nice patterns with a Pure Gold .670 shooting the same load.
Hevi-13 has come out with their 3" 2oz #7 load, and it should be a good load as well.
Of course you could just shoot Nitro #7's, and pretty much be guaranteed a good pattern.